These slides covers what is Smoke Density and hoe to measure this using Bosch type smoke meter

1. By:
Rohtash Kumar

2. Introduction:
Controlling motor vehicle emissions is important for improving air quality on urban, regional and
national scales. In response, vehicle emissions standards over the past 35 years have become
more stringent, fuel quality has improved and vehicle emissions inspection and maintenance
(I/M) programs have been implemented in areas with air quality problems in an attempt to
ensure that the emissions-control systems developed in response to these more stringent
standards remain operating throughout a vehicle’s lifetime. Because of I/M’s important role in
reducing emissions from motor vehicles, many countries are researching in this area.
Compared to harmful & invisible emissions, visible emissions are more irritating and cause
nuisance. Especially in Diesel engines, smoke is one of visible emissions. Exhaust emissions from
diesel engines are usually more visible than those emitted from petrol engines because they
contain over ten times more soot particles. In general diesel engines produce less carbon
monoxide than petrol engines but more oxides of nitrogen, oxides of sulphur (although very
little with modern low sulphur fuels), aldehydes and particulate matter.

3. What is Smoke & Smoke density??
 Smoke is a general term used to describe the cloudy, hazy, emanations that result from the
burning of organic substances. It consists of solid and/or liquid particles or droplets that
are so small that they tend to remain suspended in air for extended periods of time
s varying from seconds to years.
 The smoke of the engine exhaust is a visible indicator of the combustion process in the
engine. It is visible products of combustion due to poor combustion.
 Although smoke is often visible to the human eye,much of it is not.The size and content
of the particles or droplets comprising smoke very much affect our ability (as well as the
ability of optical instruments) to “see” it.
 A simple example of invisible smoke from everyday experience results from the act of
toasting bread. Long before visible smoke is obvious to the eye, the human nose senses
the very small particles wafting in the air. It is only later when the toast begins to
brown or blacken that the particles grow large enough to be seen as smoke.
 Opacity is a measure of light reduction/loss over a smoke column path usually expressed
as a percentage. An opacity of 10% means that 90% of the source light power remains
and 10% has been lost after passing through the measurement path. The 90% (0.9) ter
m (the light remaining) is referred to as Transmittance.

4. Smoke density
 Smoke density is a term usually associated with opacity measur
ements where there is reason to assume that the optical measur
ement relationships follow the Beer‐Lambert exponential laws.
 The Bee-Lambert Law is usually expressed as T=e-KT where T is
transmittance (which is same as 1- ), K is the smoke density factor in
units of inverse length, and L is path length of the measured smoke
sample column. Conceptually , the smoke density terms represents
the exponential light loss sensitive per unit length of the smoke
column.
 Smoke density in air is measured, like fog and smog, by having a
beam of light of known intensity a given distance away and
measuring how much light gets through. This can be done by having
the light out there or by having the light next to the measuring head
and a retro-reflector (one that returns a beam along its own path)
out there.

5. Why Smoke is there?
Main reasons for smoke in engine emissions:-
a) Incomplete combustion: -Incorrect fuel-air ratio and Improper mixing.
b) Overfilling the crankcase with oil.
c) Incorrect oil grades.
d) Operating engine at greater than a 15 degree angle.
e) Inoperative crankcase breather.
f) Crankcase air leak.
g) Blown head gasket.
h) Worn cylinder and/or rings.
i) Turning/tilting the engine on its side for storage, oil change or any other reason.
j) Injection system-Inadequate or excess penetration, unsuitable droplet sizes, excessive
duration of injection, improper dispersion atomization etc.
k) Improper maintenance of engine.
l) Fuel-More Volatile fuel gives Less smoke than heavier fuels of similar cetane number.
m) Load- A rich fuel-air mixture results in higher smoke because the amount of oxygen
available is less.

6. Types of Smoke:-
 Black Smoke - This is the most common one and is really just an imbalance in the air to fuel
ratio - too much fuel to not enough air. This means either too much fuel is being added to
the mix or there's not enough oxygen being supplied to burn the fuel. The black smoke is full
of particulates that are basically large diesel particles that normally would be burned as fuel.
Most common causes of black smoke are faulty injectors, a faulty injector pump, a bad air
filter (causing not enough oxygen to be supplied), a bad EGR valve (causing the valves to
clog) or even a bad turbocharger. Some of these are easy fixes.
 White Smoke - white smoke means that the fuel that is being injected into the combustion
chamber is not being burned properly. The common causes that produce white smoke range
from something as simple as low engine compression or water in the fuel to the fuel pump
timing being thrown off because something is starving the fuel from getting to the pump in
the manner necessary for the pump to time and work correctly.
 Blue Smoke - blue smoke results from burning engine oil. This is a mechanical problem
because engine oil isn't supposed to be getting into areas where it can be burned. There
could be a faulty injector pump or lift pump, which would allow oil to mix with fuel and be
burned. The valves or valve stem seals could be bad. Worn cylinders and piston rings can
help with this problem) allows oil to seep where it shouldn't. having put too much oil in the
engine.

7. Need to measure Smoke Density
 To find the amount of Diesel exhaust emissions contribute to ground‐level ozone
(smog), fine particulate pollution, and contain over 40 substances that are considere
d toxic.
 There are essentially two health issues associated with exposure to Diesel Engine
Exhaust Emission(DEEEs) .
 In the short term, exposure to high concentrations of DEEEs will cause irritation of
the eyes and respiratory tract. Nitrogen oxides, sulphur oxides and aldehydes are all
respiratory irritants and are present in DEEEs. It is probable that they all contribute to
the overall problem and the ultrafine soot particles may also be a contributory factor.
In the long term there is some evidence to indicate that sustained exposure to DEEEs
may slightly increase the risk of lung cancer.
 Research has shown that this is due to the fine, often ultrafine, soot particles
associated with DEEEs and the substances absorbed onto them.

8. How to measure Smoke Density?
In smoke density measurement generally following terms are used:-
 Smoke number is a term relating the output of smoke meters (aetholometers) that
measure optical properties of smoke on a filter “paper” substrate.A variety of smok
e number scales have been developed to relate different instrument measurements t
o the assumed amount of soot being measured. An underlying assumption for suc
h reporting is that soot is the majority or at least most important constituent of th
e smoke to be measured.Common reporting scales include Hartridge Smoke Unit
s (HSU), Bosch Smoke Unit (BSU), Filter Smoke Number (FSN), etc.
 Smoke Factor (SF) is a term introduced by ESPH to describe its remote sensing
measurement of smoke. It represents a ratio of exhaust opacity to the amount
of fuel burned at the time of measurement.SF is measured in the UV using frequenci
es providing the greatest sensitivity to the particulate mass fraction. The amount of
fuel burned element of the ratio is formulated by summing measurements of
the carbon‐based gases of the exhaust.For black diesel smoke, a SF of 1 indicates 1%
of fuel by mass is emitted as PM.

9. Smoke Measurement:
Smoke measurement broadly classified into two groups:
1) Comparison Method
2) Obscuration Method
1. Comparison Method- Ringlemann Chart is used in this process.
The chart shows four shades of gray as well as pure white and an
all-black section .In use, the chart is set up at eye level line with
the stack at such distance that the sections appear to be different
degrees of uniform gray shades. Ringlemann number ranging from
0( no smoke) to No. 5(dense black smoke).
2. Obscuration Method: Divided into 3 types.

10. Continue..
Obscuration Method: Divided into 3 types.
 Light Extinction type-Intensity of light beam is reduced by smoke
which is a measure of smoke intensity.
Ex. Hartridge smoke meter.

11.  Continuous Filtering Type-Measurement of smoke
intensity is achieved by continuously passing exhaust gas
through a moving strip of filter paper and collecting
particles.
Ex. Van Brand Smoke meter.

12.  Spot Filtering Type-A smoke strain obtained by filtering a given
quantity of exhaust gas through a fixed filter paper is used for
the measurement of smoke intensity.
Ex. Bosch Smoke meter.

13. What is Smoke Meter ?
 An Instrument which determines the smoke density in exhaust
gases emitted by engine systems.
 The term Smoke Meter generally refers to a smoke measuring
instrument based on optical property measurements. A wide
variety of approaches to such instruments exists.
 Many measure opacity directly through the smoke column.
Others measure opacity through a sampled fraction of the
column.

14. Bosch Type Smoke Meter
 Bosch Type Smoke Meter is Pollution Checking Machine for Diesel Engine Vehicles.
This is ARAI( Automotive Research in India)approved. This is simple and relatively
inexpensive piece of equipment for monitoring tailpipe particulate emissions.
 Construction:

15. Construction (Cont.):

16. Construction & working (Video)
Please click on above box to start the video

17. Working:

18. Procedure to measure:
The Bosch Smoke Meter consists of two parts:
1) A sampling pump- which can be inserted into the exhaust pipe
and which draws a defined quantity of exhaust through a filter
disc and this is shown in the foreground of the photograph.
2) A smoke meter evaluating unit-which photoelectronically
measures the ‘blackness’ of the sampled filter disc using a ‘light
pen’ to provide a reading (Bosch No.) of between 0.0 (white)
and 9.9 (intense black). The more soot particles present in the
exhaust emissions the ‘blacker’ the filter and the higher the
Bosch No. And this is shown at the rear of the photograph.

19. Way to control SMOKE Exposure:
 The two main way to reduce smoke level are :
a) Run at lower load, i.e. derating.
b) Maintain the engine in Best possible condition.
 Others:-
1) VEHICLE MAINTENANCE -Poorly serviced and/or badly tuned engines produce far more
exhaust emissions than well maintained engines Check the crankcase for leaks. Regular
basis check whether the head gasket blown? Are the rings and/or cylinder worn
2) ENGINE DESIGN -Manufacturers are improving the design of diesel engines all the time
and modern engines are cleaner and produce far less exhaust emissions than older
engines
3) FILTERS -There are now available catalytic diesel exhaust filters that can both trap the
particulate and, when exhaust temperature conditions are catalytically favourable , oxidise
the particulate to carbon dioxide.
4) VENTILATION -Good ventilation to dilute and disperse the exhaust emissions is possibly
the most important factor for ensuring exposure is kept to a minimum.
5) FUEL -Diesel fuels are being improved all the time to make them cleaner burning and so
reduce emissions. One major improvement has been the reduction in the sulphur content
of diesel fuel.